1. Field of the Invention
A device, such as a flexible spinal fusion cage, which can articulate or bend in such a way that it will be able to be implanted through bone (i.e., in a trans-osseous path, through bone, such as the Ilium and/or sacrum joint approach into L5-S1 is disclosed.
2. Description of the Related Art
Typical lateral approach fusion implants (e.g., Nuvasive XLIF, Medtronic DLIF) are not able to implant into some orthopedic target sites for a variety of reasons.
Boney obstacles can impair access. FIGS. 1a and 1b illustrates the challenge of gaining lateral access to L4-L5 and L5-S1. The lower spine is shown, including the L3, L4, L5 and S1 vertebra (or Sacrum) 10a, 10b, 10c and 10d, and the L4-L5 intervertebral disc space 12a, L5-S1 intervertebral disc space 12b, and the Ilium or Iliac bone 14, the Sacral ala 16, the Sacroiliac joint 18, and the Symphysis pubis 20. Note the position of the Ilium relative to the direct lateral access pathway to the intervertebral disc spaces 12a and 12b. The Ilium 14 obstructs the target site for typical approaches to the respective disc spaces 12a and 12b. 
Some doctors create large windows through the Ilium 14 to gain direct line of site access. This is a highly invasive approach removing a significant portion of bone, and requires significant surgical skill. Because of the inflexibility of the typical implants, the windows must be large enough to fit the entire implant cross section.
FIGS. 3 and 4 illustrate that the approach angle of a tissue retractor relative to the location of the fusion site is an issue. FIGS. 3 and 4 illustrate typical L4-L5 and L5-S1 approach paths 22a and 22b, respectively, for delivering the support device to the L4-L5 and L5-S1 intervertebral disc spaces 12a and 12b. The L4-L5 and L5-S1 approach angles 24a and 24b, respectively, can be measured from the transverse plane. The tissue retractor used in lateral fusion surgery provide line of site access to the disc space requiring a fusion cage insertion, the retractor “holds” tissue out of the way. They also create a working channel to pass tools through, they protect neural tissue, and they anchor to the superior and inferior vertebral bodies relative the disk space requiring fusion. Anything below the dashed line is very hard if not impossible to reach with direct lateral approach due to the Ilium. Even if the retractors are tilted as shown by the dotted line, the ability to insert an implant that is the length of the end plates of the VB's L4-L5 would be very difficult.
Furthermore, with the retractor positioned in the plane/direction as shown by the purple arrows above, the angle formed between the arrow tip and the VB's end plates would make inserting a monolithic fusion cage virtually impossible. A close up of this is shown below. A typical lateral fusion cage (gold) is the width of the end plate (a shown by the dotted lines) by the height if the disk (as shown by the parallel horizontal lines). The stiff, monolithic implant can be difficult if not impossible to turn around the corner at the lateral and/or anterior edge of the L5-S1 intervertebral space, as shown (as the bold circular dot) in FIG. 5.
Typical treatments for L5-S1 include anterior approaches, through the belly, TLIF (transforaminal lumbar interbody fusion), and PLIF (Posterior lumbar interbody fusion). Anterior and TLIF approaches are the most used. Both approaches are typically invasive.